Electric heating element and method of manufacturing same



Feb.' 26, 1929.

A. SCHMIDT"PREDARI ELECTRIC HEATING ELEMENT AND METHOD OF MANUFACTURING SAME Filed Aug. 5, 1926- Patented Feb. 26, 1929.

UNITED STATES ALBERT SCHMIDT-PREDARI, F WEIMAR, GERMANY ELECTRIC HEATING ELEMENT AND METHOD 0F MANUFACTURING SAME.

Application led August 5, 1926, Serial No.

My invention relates to electric heating elements and to a method "of manufacturing such. elements, and it is anobject of my invention to provide an element which is simple y 5 and cheap and generates a pleasant radiation.

To this end, I provide a plate or a pairof plates made `frlom inflammable fibrous material such as wood or wood substance, which has been treated so as to make it fireproof or to reduce its inflammability, and I embed the heating wire in or between the plate or plates.

The heat emitted by such an element is soft that is,m0re pleasant than the hard heat emitted from metal heating elements.

Preferably, the heating element. isY perforated in order to increase its radiating surface, and the heating-wire should be so arranged as to surround the perforations on further increases the total amount of heat which is radiated from the element.

I prefer, in manufacturing my heating element, to insert a heating wiregbetween two plates, for instance, of wood, and to exert transverse pressure on the plates so that the wire is forced into the mating faces of the plates.' This method which is ,ve-ry simple has the additional advantage that it gives a most intimate Contact for the heat transfer from the heating wire to the body of the element because the formation of cavities or open 'cracks 'is effectively preventedi', Besides, it is not necessary to forml roo'ves or other recesses in the mating faces o the plates before the heating'wire is inserted. On the other hand, grooves may be made if desired, for instance if the wire is rather thick.

- Where wood substance is used for the heating element, the intimate contact of the heat- I ing wire andthe body of the element may be obtained by the wire.

A particularly simple method of making the heating element consists in Sewing the heating wire on a plate of insulating material, or sewing it into such material, and embedding the plate on which the wire has been sewn in a definite position, into the vplatesor the wo'od substance.

. In order to obtain. a perfectly tight outer surface of the heating clement. the element,

after havingbeen finished, is impregnated casting the substance about with a substance adapted to fill itspore'sv and p lother openingse for instance, by immersion in` an agent of this kind..

It is also possible all sides, to the extent' practicable. Thisl 127,195, and in Germany January 13, 1926.

to enhance the resistance to fire in the plate, which, as mentioned, is rendered fireproof or less inflammable previous to being combined with the wire, by suitable composition of the impregnating agent.

In the drawinfrs, heating elements manufa ctured in accor ance with my invention, are illustrated by way of example.

In the drawings Fig. l is a sectional elevation of a heating element on the line I-I of Fig. 2,

Fig. 2 is a plan view of the element,

Fig. 3 is a section on the line III-III of Fig. 1, on a larger'scale, f

Fig. 4 is a reproduction of part of Fig. 3, on a still larger scale,

Fig. 5is a section through one of the per,- forations of the heating element, showing plates grooved for the reception of the heating Wires,

F ig. 6 shows separately the lower plate, i.

Fig. 7 is a plan View of this plate, showing part of the heating wire in position,

Figs.'8 and 9 are a cross section/andy an elevation of a wire coated with insulating material,

Fig. -10 1s a plan View of a plate of insulating material with heating wire sewn thereon,

Figs. 11 and 12 are plan views of modified heating elements.

` Referring first to Figs. 1to 4, the element consists of two plates 1, 2, of wood or the like', pporting strips for the lower plate 1, and s the heating wire. After this wire has been inserted between the plates 1 and 2, the plates are forcedtogether and connected by 'an adhesive or similar means, if desired. Registering perforations are formed in the upper and lower` plates at 5 which extend through both plates. The object of these perforations is to increase the heat radiation. If desired, they may be made in one of the plates only or each plate may be recessed i-nstead of being perforated.

Fig. 2 shows the arrangement of the heat- `loo ing wire within the finished element. 4 is the wire. 6 is a line wire supplying current, and 7 .is a plug or the like.

The wire 4 may be provided with an insulatin layer 8 as shown in Fi s. 8 and 9 and 105 may e embedded with or witfliout this layer between plates 9 of mica inserted between the lates 1 and 2, as shown in Figs. 3 and 4.

Fig. 10 shows an insulating plate 11` on which the wire 4 is sewn by means of a thread.- llo 10 and the plate with the wire is inserted between the plates 1, 2. If desired, mica plates 9 may be used in this case, as described.

If the Wire 4 is very thick, theny plates 1 and 2, or one of them, may be grooved at 12, as-shown in Figs 5 lto 7 The element shown in Fig. 11 is of substantially rectangular shape, with rounded edges at both ends. The heating wire is so arranged that its `windings intersect and sur- 1. A heating element comprising a base of inflammable reproofed poor heat conducting material and a heating wire snugly embedded in said base. Y

2. A heatin element comprising a base of inflammable reproofed poor heat condcting material, a heating'wire snugly embedded in said base, and an insulating layer inserted between said Wire and sa1d base. v

' 3. A heating element comprising a base of `normally infiammable material which has been fireproofed, said `base being provided with perforations passing through the same and occupying a predetermined arrangement therein, and a heatin wire embedded in said` e base so as to follow t e arrangement of said perforations. v v

4. A heating element comprising a base of normally inflammable material which has been fireproofed., said base being provided with perforations passing through' the same and a heating wire embedded in said base in the Vicinity of said perforations.

5. A heat-ing element comprising a base of normally inflammable materialV which has been fireproofed, said base being provided with recesses in a surface thereof, and a heating Wire embedded in said base in the vicinity of said recesses.

6. A vheating element comprising two parallel plates of infiammable fireproofed material, and-a heating Wire embedded between said plates.

7. Method of manufacturing heating elements consisting in inserti-nga heating wire between tWo plates of inflammable fireproofed poor heat conducting material and exerting pressure on said plates to force said Wire into said plates. v

8. Method of manufacturing heating elementsconsisting in forcing a heating wire into a plate of inflammable fircproofed poor heat conducting material by pressure.

9. Method of manufacturing heating elements-consisting in securing a heating Wire to a base of insulating material and combining said Wire and its base with a plate of inflammable ireproofed poor heat conducting material by pressure.'

v10.. Method of manufacturing heating elements consisting in forcing a heating 'Wire into a plate of inflammable fireproofed matcrial by pressure, and impregnating said plate With an agent adapted to fill its pores and other cavities. e

In testimony whereof I affix my signature.

ALBERT SCHMIDT-PREDARI. 

